bool isPalindrome(char * s){
    int i = 0,j = 0;
    while(s[i]){
        if(s[i] >= 48 && s[i] <= 57)
            s[j++] = s[i];
        else if(s[i] >= 65 && s[i] <= 90){
            s[i] += 32;
            s[j++]= s[i];
        }
        else if(s[i] >= 97 && s[i] <= 122)
            s[j++] = s[i];
        i++;
    }
    int left = 0,right = j - 1;
    while(left < right){
        if(s[left] != s[right])
            return false;
        left++;
        right--;
    }
    return true;
}

